Here are the main points so far from the debate over whether to extend from 14 days to 90 days the length of time police can detain terrorist suspects without charge:

Home Secretary Charles Clarke opens the three hour debate by outlining the government's amendment relating to the "complex and contentious question of pre-charge detention".

He said he had spoken to Sir Hugh Orde, Chief Constable of Northern Ireland, who was "unequivocal that this legislation was, from his experience and from his point of view, necessary, including the extension to 90 days".

Mr Clarke stressed that anyone detained beyond the current 14 day maximum would have their case reviewed by a High Court judge every seven days.

Senior Tory backbencher Sir Patrick Cormack asked if the home secretary had spoken to any other chief constables in the UK who supported the extension to 90 days.

Mr Clarke said he had not spoken to all the chief constables, but those that he had, supported the plan.

Shadow home secretary David Davis, whose party says they will support a lengthening of the detention limit to a maximum of 28 days, suggested an alternative of allowing police to interview a suspect after they were charged to "open up a good deal of evidence to them which will actually act to stop terrorism".

Mr Clarke said he agreed, but "it does not remove the need for pre-charge detention in a limited number of circumstances".

Ex-Cabinet minister Clare Short argued that the police already have powers to apply for further time to question a suspect if new and significant evidence emerges.

Ex-minister Joan Ruddock said the prime minister "has sought to make this debate a simple matter of party politics" which some Labour MPs do not agree with.

Mr Clarke said he did not agree. "I think it is an inaccurate description of the state of affairs," he said.

He said after meetings with the senior members of the two main opposition parties it was clear that in "no circumstances" would they consider extending the period of detention beyond 28 days.

He said that he had decided "against all my better instincts, because I am not a fan of sunset clauses" adding one to the bill, which would mean the 90-day plan would run-out after 12 months. He said he hoped this might address MPs' concerns.

Tory leader Michael Howard reminded Mr Clarke that after his meetings with the opposition parties he had suggested that he would be tabling an amendment to the bill "for a lower period of detention".

Mr Clarke agreed that he had said that.

Mr Howard said he had asked the prime minister "months ago" for a briefing to test whether it was "indeed the case that had a 90 day period been in place it would have led to the apprehension of people who would otherwise not be apprehended".

Mr Clarke said the case was "compelling" for the 90-day plan.

But Ex-Tory chancellor Kenneth Clarke accused the home secretary of "plucking a figure out of the air".

Charles Clarke responded that MPs should take "extremely seriously" the professional judgment of the police and the prosecutors who are calling for the 90-day plan.

Labour MP Tony Wright said Lord Carlile, a QC and Liberal Democrat peer appointed by the government to review its anti-terrorism legislation, had said the maximum three month detention was "probably a practical and sensible" length of time "all things being equal".

Ex-minister John Denham warned Mr Clarke not to "over-state the case" for 90-days.

Labour backbencher Madeleine Moon asked why police in this country needed "powers that are not being taken in other European countries in particular in Spain", which had also experienced terrorist attacks.

Mr Clarke argued that Britain was facing a different type of terrorism now, designed to cause mass casualties, with no warnings, often involving suicide bombers and the threat of chemical and biological attack.

He said advisors from the National Technological Assistance Centre, who deal with encrypting computers, had told him that a 14 or 28 day detention period "will not allow them the time they need to investigate encrypted data".

Labour MP Mark Fisher said locking up people for 90 days, with the possibility of being released without charge, could send "martyrs" back into communities.

Mr Clarke said this was "totally wrong". Friends in the Muslim community were clear they "want no part in this terrorism" and do not want to be identified with it, he said.

He urged MPs to "think hard" about the decision they make when voting on the 90-day plan on Wednesday evening. He said the House should not duck its responsibility.

Shadow home secretary David Davis said his party had friends and colleagues who had been murdered by terrorists, including MPs Airey Neave and Ian Gow. "This party has had first hand experience of terror," he said, and it was wrong to suggest it was "soft on terrorism".

He said what the government was talking about was "imprisonment without trial" in the country that invented Habeas Corpus.

Mr Davis said his party had tried to be helpful "within the limits of the duties of this House ...to protect the liberties of the British subject" to support the government in its fight against terrorism.

Ex-Tory Cabinet minister John Gummer said it was for the Commons to decide how best to meet the needs which the police bring forward, "not for the police to tell this House how to legislate".

Mr Davis agreed: "Liberties shouldn't be thrown away on the judgement of people who have got a task to do."

Tory Angela Watkinson asked if it was timely that during a cross-party visit to South Africa, the group were taken on a tour of Robin Island, where Nelson Mandela was incarcerated for 27 years, by a former prisoner who said: "This all happened when we used to lock people up for 90 days without charge."

Mr Davis said Tony Blair believed the "case is compelling" for the 90-day detention, like he believed the case was compelling for weapons of mass destruction in Iraq. "Like weapons of mass destruction - it is not there," he said.

He challenged anyone to show him how a single terrorist incident would have been prevented by the 90-day detention plan.

Lib Dem deputy leader Sir Menzies Campbell criticised people who described as "pathetic" those who objected to the 90 days on a point of principle.

He pointed out that current Labour ministers had opposed terrorism measures on principle many times when they were in opposition during the last Conservative government.

Ex-Tory minister Robert Key said he deplored the way chief constables, like Met chief Sir Ian Blair, had been brought into a political debate.

Mr Davis said: "The case for 90 days has not been proved beyond reasonable doubt. It will doubtless be argued that what the police want, the police should have." He said what was there to stop the police from coming forward to ask for detention lengths of 100 days or two years.

He added that the bill "will be counterproductive", and might "turn out to be a gift to the terrorists".

Veteran Labour MP David Winnick, who will put forward a 28-day proposal if the Commons rejects the government's amendment, said a balance needs to be struck between traditional liberties, rule of law and trying to protect this country from acts of terror.

"The right not to be imprisoned without being charged, not to be subject to arbitrary arrest and habeas corpus are all basic to our democracy," he said.

He asked his fellow MPs how they would like to be locked up for 90 days if they were innocent.

He conceded that opinion polls showed more popular support for 90 days rather than 28-days, but said: "If the time ever comes that the House of Commons decides issues, not on the merits, but the latest opinion polls ...we might as well pack in and go home."

He appealed to MPs: "If you do have hesitations, that you feel on balance 90 days is excessive, I urge you, don't go in the division lobby and vote on what you don't believe in."

Alistair Carmichael, a home affairs spokesman for the Liberal Democrats standing in for Mark Oaten, asked why the Lord Advocate, Scotland's top lawyer, had not been asked to give a view on the suitability and workability of the 90-day detention plan.

He said of the measures: "This is no flight of fancy because we have been here before - detention without charge is not a new concept. We tried it in Northern Ireland - we know what the consequences of that were."

He said MPs have to oppose the government's 90-day plan if they want to have the opportunity to support Mr Winnick's 28-day proposal.

"There is no principle that says 14, 28 or 90 days is right. The principle that is at stake is nobody should be deprived of their liberty unless there is evidence in which to do so," he said.

"It must be important that if we do move to 28 days there are necessary locks and safeguards put in place."

Labour's Claire Curtis-Thomas urged MPs to back the home secretary, who she said was seeking support following advice from the police.

Tory Michael Mates, a member of the intelligence and security committee, said the government should have explained the complexities of the police and security services' advice and why they had reached the conclusions they had.

But he said he would not be voting against the government's proposal because he thought the 28-day alternative inadequate.

However, veteran Liberal Democrat Alan Beith cautioned him not to suggest that there was evidence out there that would force anyone who saw it to come to a different conclusion.

Mr Mates said the government had "got themselves into this mess and they have got to get themselves out". He said the explanations given by ministers were "too little, too late".

Tory MP Ben Wallace, who has served in Northern Ireland with the Scots Guards, warned the government not to take "short cuts to counter terrorism".

He said the government had failed to present a case that would persuade people of the necessity for 90-day detention.

It was "entirely bogus" to suggest that 90 days was needed for the encryption of computers. There had been cases where experts had failed in two years to unlock devices, he said.

He said if this "short cut" was taken he was almost certain MPs would be back debating the issue again because there would still be bombs on the Underground and terrorist attacks "because the causes are still here".

Ex-minister John Denham, chairman of the Commons home affairs select committee, said the prime minister and other ministers had made more effort trying to win the votes of MPs on this issue "than we have had in winning the hearts and minds of young Muslims".

"I think the handling of this issue has actually done damage to the fight against terrorism," he said.

No effort had been made to give the "most basic explanation from the police about why 90 days was needed", he said.

He said the prime minister had backed the plan on the basis of a press release from ACPO (the Association of Chief Police Officers) and two sides of A4 which detailed two cases. He added that "neither made the case for 90 days".

"It is my personal view that had that proper assessment taken place it would actually have supported an extension period that went beyond 28 days," he said.

"I will vote for 90 days tonight because the case is between that and 28 days," he said.

He added that he would be asking his select committee to launch an inquiry into the police advice.

Senior Labour backbencher Janet Anderson, who has tabled a "fall-back" position of 60 days said she would be supporting the 90-day plan.